Apparatus and method for election beam evaporation

ABSTRACT

An electron beam evaporator, which is formed of the component assemblies: beam generator, deflection system and water-cooled crucible/rotary crucible, is fastened on the cover plate of a flat hollow body.  
     The hollow body is placed gas-tight on a bore in the tank and can be turned about the main axis of the bore. The interior of the hollow body is connected with atmosphere through the bore. All connecting lines for water, low-voltage current, high voltage and rotary drive are carried in the hollow body to the component assemblies which are mounted gas-tight.

[0001] The invention relates to an electron-beam evaporator for vacuum coating apparatus as used, for example, in optics for tempering lenses or eyeglass lenses. For this purpose the substrates to be coated are moved on an appropriate substrate holder over the vapor source heated by the electron beam, and are thus coated. The evaporation point from which the vapor is released is usually off-center from the main axis of rotation of the substrate holder.

[0002] The multiplicity of different substrate shapes and surface curvatures call for special efforts to achieve the desired coating thickness tolerances and coating thickness distribution within a batch on the substrate holder in the vapor coating apparatus. Another difficulty consists in the various evaporation characteristics of the coating material in use. For this reason it is desirable to have a variable or adjustable positioning of the evaporation point with respect to the substrates being coated, so that an optimum evaporator position can be set for each substrate form and each coating material.

[0003] An electron beam gun that is movable within the vacuum is disclosed in German Auslegeschrift 21 18 082. A container to which the electron gun is fastened is connected to the atmosphere through a tube. The electron gun is part of the container wall. The tube is guided in the chamber wall and is longitudinally displaceable. Such an apparatus is not suitable for use in optical coating, since it is too expensive. The variable range for the positioning of the evaporation point in optical coating apparatus of the prior art is only around 0.05 to 0.5 m. Furthermore, the vapor coating of the tube and the contamination of the optical coating by the hydraulic oil are troublesome.

[0004] In DE 28 49 933 an electron beam evaporator is described, which is composed of the three elements: radiation source, deflecting magnet and the mounting for the material to be evaporated. The three component elements are displaceable in their spacing from one another, so that the evaporator is adaptable to the particular application.

[0005] In DE 37 04 505 an insertion device for vacuum apparatus is described, which has a bipartite, jointed lever arm the inner part of which is configured as a gas-tight hollow body and contains the driving means for moving the insertion arm.

[0006] The invention is addressed to the problem of installing an electron beam evaporator into a vapor coating apparatus such that the evaporation point can be adapted with little difficulty to various vapor coating conditions and substrate shapes without the need to remove the necessary connections and connecting lines.

[0007] The solution of the stated problem is accomplished by the invention in that:

[0008] a) The support plate is configured as a cover plate of a flat hollow body whose interior is in communication with the atmosphere through a bore in the tank.

[0009] b) The hollow body is placed over the bore in the tank such that it can be turned about the main axis of the bore.

[0010] c) The component assemblies of the electron beam evaporator are placed vacuum-tight on the mounting end of the hollow body.

[0011] d) All the connecting lines are carried through the interior of the hollow body to the component assemblies.

[0012] The invention makes it possible to optimize the evaporation point for every coating operation in a simple manner. By merely releasing the clamping ring the evaporator can be rotated about the main axis of the bore and thus achieve an optimum distribution of the coating thickness on the substrates.

[0013] With additional effort, an in situ adjustability without interrupting the vacuum might be possible, or even the intentional oscillation of the evaporation point by a rocking movement.

[0014] The apparatus of the invention is represented in FIGURE. 1. The base plate 1 of the tank has a bore B which serves to hold the entire apparatus. By means of the chamber flange 5 and counter-plate 4 the bearing plate 2 is inserted into the bore B such that the bearing plate 2 can be rotated about the central axis A. A cover plate 3 of channel-shaped cross section is placed on the bearing plate 2 in a vacuum-tight manner by means of the gasket 13′. The hollow space formed is in communication with the atmosphere and serves to accommodate the drive means and supply lines. The individual modules of the electron beam evaporator are sealed hermetically by O-rings on the upper, vacuum side. These modules are the deflecting unit 6 for x and y axis deflection of the electron beam, the cathode unit 7 with exchangeable beam generators, and the base unit 8 with exchangeable crucible 10.

[0015] The permanent magnet 12 protected by the cover plate 21 is let into the base unit 8 and produces the main magnetic field through pole shoes, not shown, for beam deflection. The rotary crucible 10 has a plurality of recesses which are protected by the cover plate 14 against undesired vapor deposition. The rotary crucible is driven in a known manner through cogbelts by the sprockets 19 and 20 and a drive connected to the shaft 16. A sealing ring 11 forms the vacuum gasket. The connecting lines for water 15, deflection current 17 and high voltage 18 are passed through the bore B and corresponding openings in the cover plate 3 to their connection points. Since the connecting lines are in fixed positions on the atmosphere side within the hollow body formed by the bearing plate 2, the entire apparatus can be turned about the main axis A without the need to disconnecting them.

[0016] By means of the length of the bearing plate 2 the apparatus can be adapted conveniently to the different receptacle diameters. The radial position of the evaporator with respect to the substrate cup can be adjusted conveniently through the turning angle. This is important for achieving a quick optimation of the coating thickness distribution. 

1. Electron beam evaporator for installation in a vacuum apparatus with variable positioning, consisting of its known component assemblies: beam generator, deflection unit and water-cooled evaporation crucible with or without rotary drive, the fixed vacuum leadthroughs for the connection of cooling water, high voltage, low voltage current and crucible drive and the corresponding connecting lines, and a lever-like carrier plate which is mounted for rotation about an axis and the electron beam evaporator is mounted on its holding end, characterized in that a) The support plate is configured as a cover plate of a flat hollow body whose interior is in communication with the atmosphere through a bore in the tank. b) The hollow body is placed over the bore in the tank such that it can be turned about the main axis of the bore. c) The component assemblies of the electron beam evaporator are placed vacuum-tight on the mounting end of the hollow body. d) All the connecting lines are carried through the interior of the hollow body to the component assemblies.
 2. Apparatus according to claim 1 , characterized in that the component assemblies, for example the beam generator, are of multipartite construction and are exchangeable by plug-in connection without removing the vacuum seal on the carrier plate.
 3. Method according to claims 1 and 2, characterized in that the evaporator position is varied during or between applications of a coating. 